Autism spectrum disorder (ASD) refers to a range of developmental disabilities characterized by challenges with social skills, communication, restricted interests, and repetitive behaviors. ASD is considered a developmental disorder, meaning that the onset of symptoms occurs during early childhood. However, there is some debate around whether a child can suddenly develop autism later in childhood or even in adolescence.
What is the typical onset of autism symptoms?
The majority of children with ASD show some signs of the disorder by age 2 or 3. Early signs may include reduced eye contact, lack of interest in other children, delays in language development, excessive focus on certain objects or topics, and excessive repetition of words or actions.
According to the DSM-5 diagnostic criteria, symptoms must be present in early childhood for a diagnosis of ASD, even if they are not fully recognized until later. This reflects the understanding that autism is a developmental disorder that arises early as the brain is forming.
Is sudden onset autism possible?
While autism is typically viewed as a condition that emerges gradually in early childhood, some parents have reported what appears to be a sudden onset of autism symptoms in their child. There are a few possible explanations for these anecdotal reports:
- Missed early symptoms – Subtle early signs of ASD may have been overlooked or mistaken for normal developmental variations. Apparent sudden onset may reflect when symptoms became too pronounced to ignore.
- Regression – Children who appear to be developing typically but then lose skills and show ASD symptoms between 18-24 months. This regression may appear abrupt but reflects an underlying developmental process.
- Unmasking – Gradual developmental difficulties finally exceed limited compensatory skills. The child can no longer cope with social or behavioral expectations.
- New triggers – Changes in environment, stressors, or biological factors unmask an underlying condition and lead to rapid deterioration in function.
In most of these cases, the child likely had an underlying developmental disability, even if subtle, from early on. While the onset or worsening of symptoms may seem sudden, it does not reflect the actual origin of the condition.
Are there any exceptions?
There are a few rare circumstances in which a regression or sudden onset of autism-like symptoms could potentially happen later in childhood:
- Childhood disintegrative disorder – Extreme regression and skill loss after 2-3 years of typical development. This is an extremely rare condition distinct from autism.
- Head injury – Traumatic brain injury has very rarely been associated with acquired symptoms of autism following normal development initially.
- Encephalitis – Neuroinflammation from severe infection is hypothesized to sometimes trigger onset of autism-like symptoms later than the typical age window.
However, most experts believe these situations do not represent a “true” sudden onset form of autism. Rather, they are unique medical conditions that can result in developmental regression or neurological symptoms that may resemble aspects of ASD.
What do studies show?
Several large-scale studies provide insight into timing of autism onset:
| Study | Findings |
|---|---|
| Christensen et al. 2016 | In a Danish cohort study of over 600,000 children, 90% showed signs of ASD by age 3, even if not diagnosed until later. |
| Ozonoff et al. 2018 | A US study of over 2000 children found 95% had developmental concerns by 24 months, even if parents did not recognize them as ASD symptoms. |
| Barger et al. 2013 | Among nearly 1000 children with autism, regression of skills almost always occurred between 12-24 months and was distinct from definite sudden onset autism after normal development. |
Overall, these population-based studies reinforce that autism arises and is detectable in the first few years of life, even if a firm diagnosis takes longer. Apparent sudden onset cases likely reflect other circumstances like missed subtle early signs or distinct medical conditions.
Can late onset autism be missed diagnosis?
In some cases where autism appears to emerge later, it may represent a missed diagnosis earlier in childhood. Reasons this could happen include:
- Milder symptoms early on that go unrecognized
- Lack of developmental screening and monitoring
- The ‘camouflaging’ phenomenon in higher functioning children
- Compensation strategies and coping mechanisms obscuring symptoms
- Symptoms mistaken for other conditions like ADHD
- Reliance on parent reporting versus direct clinical observation
Therefore, some children who seem to suddenly develop autism in late childhood may have had underlying ASD that was not identified until the child faced greater social, behavioral, or academic demands.
Can teenagers or adults be diagnosed with autism?
Autism spectrum disorder is considered a neurodevelopmental condition that arises in early childhood. Typical diagnostic criteria require symptom onset during early development. Nonetheless, some individuals do receive initial ASD diagnoses as teenagers or adults. Explanations include:
- Missed childhood diagnosis later recognized
- Failure to meet full diagnostic criteria earlier
- Gradual unmasking of an underlying condition
- Misdiagnosis with similar conditions like social anxiety earlier
- Developmental history unavailable from childhood
While unusual, it is possible for an individual to reach adolescence or adulthood before receiving a formal ASD diagnosis. However, this late diagnosis reflects lack of recognition earlier in life rather than adult onset of autism.
What about Asperger’s syndrome diagnosed in adulthood?
Asperger’s syndrome was previously a separate diagnostic subtype of higher functioning autism. Individuals with Asperger’s are often diagnosed later than those with more severe autism symptoms. However, current criteria do not distinguish Asperger’s from ASD. Like other forms of autism, it arises in early development:
- Motor, language, and cognitive skills develop normally at first
- Subtle social and communication difficulties are often present in preschool years
- Intense interests and repetitive behaviors emerge in childhood
- Challenges become more apparent by upper school years
While initial diagnosis may wait until adolescence or adulthood, experts emphasize Asperger’s reflects a developmental condition present from early in life. It does not represent adult or sudden onset of autism-like difficulties.
Can other conditions mimic sudden autism?
While autism itself does not arise suddenly, there are some medical conditions that could result in autism-like symptoms developing later in childhood. These include:
- Childhood disintegrative disorder – Extreme regression between ages 2-10 after normal development.
- Landau-Kleffner syndrome – Rare childhood neurological disorder with language regression.
- Epileptic encephalopathy – Epilepsy beginning in childhood that impairs brain function.
- Schizophrenia – Onset of psychosis in late adolescence. May include social withdrawal and behavior changes.
- Selective mutism – Severe social anxiety manifesting as lack of speech only in some situations.
While these developmental and psychiatric conditions can have features resembling sudden autism, they would involve other symptoms not typical of ASD. Obtaining an accurate diagnosis is important to differentiate autism from mimics.
Can late onset autism be childhood dementia?
Childhood disintegrative disorder and regressive autism are sometimes referred to as childhood dementia, dementia infantilis, or Heller’s syndrome. These terms suggest normal development followed by loss of skills and functioning. However, research indicates these conditions likely reflect autism spectrum disorders with undetected earlier abnormalities. True sudden onset dementia without prior developmental concerns is vanishingly rare in children.
Is temporary autism possible?
There are very few substantiated cases of children developing autism that then resolves or improves dramatically. Autism spectrum disorder is considered a lifelong neurodevelopmental condition, not a temporary syndrome. However, a couple potential explanations for autism-like symptoms resolving include:
- Misdiagnosis – Symptoms resembling ASD are attributed to another source like language disorder or intellectual disability.
- Intervention – Early applied behavior analysis or relationship-based therapy results in apparently lost skills re-emerging.
- Maturation – Limited compensation skills finally emerge, masking underlying deficits present from early on.
Apparent temporary autism likely represents an initial misdiagnosis, intensive early therapy, or developmental maturation finally compensating for deficits. It does not reflect transient autism per se.
Can autism develop from vaccine injury?
There is no scientific evidence that childhood vaccinations cause autism, even though this is a common parental concern. Large epidemiological studies show no difference in autism rates between vaccinated and unvaccinated children. Cases of apparent sudden onset autism following vaccination are likely due to coincidence rather than causation. Possible reasons include:
- Early subtle symptoms amplified by stress of shots
- Normal timing of diagnosis at ages vaccines given
- Association with regression between ages 1-2 when shots occur
- Fixation on vaccines as an explanation when disability emerges
Development of autism following vaccinations reflects temporal association rather than causal relationship. Vaccines remain vital for children’s health and do not appear to trigger autism.
Conclusion
While autism spectrum disorder is sometimes perceived as arising suddenly, extensive research indicates onset of symptoms or atypical development within the first years of life. Most children with autism exhibit some signs before age 3, even if subtle. Apparent sudden onset likely reflects undetected subtle early signs, distinct medical conditions, or misdiagnosis rather than abrupt autism later in childhood. Autism reflects a neurodevelopmental process arising in early brain development, not a condition acquired later in life.
